Electron discharge device having a rotatable cathode therein



E. ATTI March 28, 1967 ELECTRON DISCHARGE DEVICE HAVING A ROTATABLE CATHODE THEREIN 4 Sheets-Sheet 1 Filed March 23, 1964 H IHHII INVENTOR Eros Afli ATTORNEY E. ATTI March 28, 1967 ELECTRON DISCHARGE DEVICE HAVING A ROTATABLE CATHODE THEREIN Filed March 23, 1964 4 Sheets-Sheet 2 7 \\\\D 6 r f A 3 lH 4 4 6 QB 2 2 5 L 0L L 2 M 0m bm 2 E 55 DE B B B March 28, 1967 E. ATTI 3,311,774

ELECTRON DISCHARGE DEVICE HAVING A ROTATABLE CATHODE THEREIN Filed March 25, 1964 4 Sheets-Sheet 3 CATHODE THEREIN E. ATTl March 28, 1967 ELECTRON DISCHARGE DEVICE HAVING A ROTATABLE 4 Sheets-Sheet 4 Filed March 23, 1964 \BIMETAL United States Patent C) ELECTRON DESQHARGE DEVICE HAVING A RUTATABLE CATHQDE THEREIN Eros Atti, Horseheads, N.Y., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 23, 1964, Ser. No. 353,633

29 Claims. (Cl. 313-146) This invention relates to improved electron device structures and more particularly to cathodes in which the cathode emissive portion may be renewed.

A problem has existed in cathode ray tubes and other similar electronic devices where after a short period of operation, the drawing of current from the cathode ultimately deteriorates the emissive surface of the cathode. In time the emissive surface is thereby impaired and the intensity of emission decreases thus afiecting the concentration of the cathode beam. Such deterioration tends to occur more readily when the current drawn from the cathode is in excess of the current emission capabilities of the cathode, namely under severe cathode loading conditions. It also tends to occur when the environment in which the cathode operates is unfavorable such as under poor vacuum conditions.

It has been suggested that the cathode element could be rotatably mounted with respect to a screen member having an aperture therein, whereby the cathode element could be rotated with respect to the aperture thereby changing the portion of the cathode from which the current is drawn and thereby increasing the life of the cathode. However, these devices have involved rather complicated means for rotating the cathode element. In particular, these devices have used complicated motor induction means to rotate the cathode. Besides being more complex and expensive, these devices have necessitated mounting means exterior to the vacuum tube envelope to properly position the induction means with respect to the cathode element within the envelope of the vacuum tube. They also create problems due to stray magnetic and electric fields associated with the induction means.

It is therefore an object of the present invention to provide an improved and longer lasting discharge device.

Another object is to provide an improved cathode assembly with an emissive portion of the cathode which can be changed from time to time to effect a longer life of the discharge device.

Still another object of this invention is to provide an improved electrode assembly and a means for changing the relative position of one of the elements of the assembly which is inexpensive to manufacture and which can be installed within the envelope of the discharge device.

A further object of this invention is to provide a simplified mechanism for motivating an electrode comprising either a thermal-responsive or magnetically-responsive stepping mechanism.

A still further object is to provide a simplified mechanism for rotating or orbiting an electrode, automatically as the discharge device is turned off and on.

Briefiy, the present invention accomplishes the above cited objects by providing a movably mounted electrode and a simple, inexpensive means for moving said electrode. More specifically, a grid or control element which has been positioned between the cathode and an anode surface is provided with an aperture over-shadowing a portion of the cathode. Thus by rotating or displacing transversely the cathode, the various emissive portions of the cathode may be positioned beneath the aperture thereby replacing a worn or dissipated portion with a new portion. In particular, this invention teaches the use of very simple thermal responsive or magnetically responsive elements for rotating or displacing the surface 3,311,774 Patented Mar. 28, 1967 of the cathode, and additionally, the use of thermal responsive elements to lock the cathode in a fixed position as long as it is desired to keep a given cathode emitting surface supplying the electron beam required for the operation of the device.

Further objects and advantages of the invention will become apparent as the following description proceeds and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention reference may be had to the accompanying drawing, in which:

FIGURE 1 illustrates an electron tube embodying the teachings of this invention;

FIGI 2 is a sectional view of the cathode assembly which is incorporated into the electron tube of FIG- URE 1;

FIG. 3 is a cross-sectional view of FIG. 2 taken along the line IIIIII of FIG. 2;

FIG. 4 is a sectional view of one modification of a detail of the cathode assembly shown in FIGS. 2 and .3;

FIG. 5 is a cross-sectional view of still another embodiment of the invention;

FIG. 6 illustrates a sectional view of another embodi: ment of this invention;

FIG. 7 shows a view of another cathode assembly comprising one embodiment of this invention;

FIG. 8 shows a cross-sectional view taken through lines VIIIVIII of FIG. 7;

FIG. 9 illustrates a view showing another means for rotating the cathode assembly shown in FIGS. 7 and 8;

FIG. 10 shows still another means for rotating the cathode assembly comprising another embodiment of this invention;

FIGS. 11 and 12 show respectively a sectional and an isometric view of an automatic embodiment of the cathode assembly in accordance with the teachings of this invention; and

FIG. 13 shows another embodiment of an automatically renewing cathode.

FIGURE 1 shows a cathode ray tube 10 as a particular embodiment of this invention. The cathode ray tube 10 comprises an evacuated envelope 11 of a suitable material such as glass with an elongated portion 12 and a flared portion 13. An electron gun 14 is mounted axially within the elongated portion 12 so that a beam of electrons emanating from the electron gun 14 will strike a target 17 coated upon the end portion of the envelope 11. Through the elongated portion 12 of the envelope 11, there are mounted terminals 18 for providing electrical signals to the various elements within the envelope 11. The electron gun 14 includes accelerating and focusing elements 15 and 16 and also a cathode assembly 20 which comprises the essence of applicants invention. A deflection means of either the electromagnetic or the electrostatic variety may be mounted outside or inside the envelope 11 respectively so as to control the deflection of the electron beam emitted from the electron gun 14.

Referring now in detail to FIGS. 2 and 3, the cathode assembly 20 has a hollow cylindrical grid cup or central element 22 made of a suitable material such as stainless steel. Disposed within the grid cup 22 and offset from the center axis of the grid cup 22 there is provided a hollow cathode shell or cylinder 24 made of a suitable material such as nickel. A cathode heater 36 is provided within the hollow cathode shell 24 to heat the cathode shell 24 and to excite the emission of electrons. A plurality of protrusions 25 are provided to firmly secure a ceramic disc 28 positioned about the cathode shell 24. The cathode shell 24 is spaced from the closed end of the grid cup 22 by a spacer 30. On the opposite side of the ceramic disc 28 from the spacer 30, there is positioned a support member 26 which is secured in a fixed position as by welding to the inner side of the grid cup 22. It is noted that the spacer 3G and the support member 26 are annular members and hold the circular ceramic disc 28 between them in place. A plurality of guide stops 31 are located on the bottom portion of the spacer 30 in an array which conforms to the circular edge of the ceramic disc 28 so that the ceramic disc 28 and the cathode shell 24 are held in an offset position from the center axis of the grid cup 22. The guide stops 31 may be secured to the spacer 30 by welding or by bending a plurality of tabs downward therefrom. On the outside of the closed end of the cathode shell 24, there is provided an electron emissive layer 23 as a means for producing an electron beam. Such a layer may be made of any of the well known electron emissive oxides such as those of barium, strontium, and calcium. Through the enclosed end of the grid cup 22, there is centrally located a grid aperture 34 which overshadows a portion of the emissive layer 23. In one embodiment to be used in a typical cathode ray tube, it has been found practical to make the diameter of the cathode shell 24 about .125 inch and the grid aperture 34 about 0.025 inch; further, the emissive coating 23 is spaced approximately .003 inch to .005 inch from the enclosed end of the grid cup 22.

As stated above, the spacer 3t) and the support member 26 position the ceramic disc 28 and the cathode shell 24 in a fixed position relative to the grid cup 22; the spacing of these elements is such as to prevent any vertical motion (as illustrated in FIG. 2) of the ceramic disc 28 but yet to allow the ceramic disc 28 to rotate under the application of a suitable torque. A very simple and inexpensive motivating means is provided by an elongated bi-metallic element 38, the fixed end (not shown) of which is secured within the envelope 11. The other end of the bi-metallic element 38 is provided with a hook-like engaging end 39 which is left free to fiex when the bi-metallic element 38 is energized. As more clearly shown in FIG. 3, the ceramic disc 28 has a plurality of ratchet teeth 42 about its periphery. A portion of the ceramic disc 28 extends through a slot 41 in the grid cup 22 so that the hook-like engaging end 39 of the bi-metallic element 38 will engage with the ratchet teeth 42. Further, a heating element 40 is placed in thermal relationship with the bi-metallic element 38. When the heating element 40 is energized, the bi-metallic element 38 will flex so as to cause the engaging end 39 to mesh with one of the ratchet teeth 42 and to apply a rotating torque to the ceramic disc 28 and the cathode shell 24 causing the ceramic disc 28 to undergo an angular movement.

In operation of the electron device, the cathode heater 36 positioned within the cathode shell 24 is energized; the heat therefrom excites the emissive layer 23 to produce electrons part of which are drawn through the grid aperture 34. After a period of operation, that portion of the emissive coating 23 directly beneath the grid aperture 34 becomes dissipated and the characteristics of the electron tube will thereby be adversely affected. In this cathode assembly 20, the portion of the emissive layer 23 beneath the grid aperture 34 may be renewed simply by energizing the bi-metallic element 38 as described above. Due to the fact that the center axis of the cathode shell 24 has been offset from the center axis of the grid cup 22, when the cathode shell 24 is rotated the shadow cast by the grid aperture 34 upon the emissive layer 23 will resemble an annular umbra 44 (indicated in FIG. 3). Therefore, during its initial operation a first emissive portion 44a would be dissipated; after rotating the cathode shell 24, a second emissive portion 44b would be placed beneath the grid apertures 34. Therefore, the electron emissive portion of the emissive layer 23 may be continually renewed until the entire umbra 44 has been dissipated. In this manner, the life of electron tube device may be substantially extended.

FIG, 4 shows a partial sectional view of a detail of the cathode assembly 20 in which the friction between the ceramic disc 28 on the spacer 30 and the support member 26 has been reduced by the insertion of ball bearings 48 into grooves 46 within the ceramic disc 28. For assembling convenience, the ball bearings 48 made of a suitable material such as stainless steel can be temporarily glued to the ceramic disc 28 by a thin lucite film to be baked out during the tube processing.

In FIG. 5, a different method has been chosen to reduce the friction of the ceramic disc 28 against the spacer 30 and the support member 26 when it is desired to renew the emissive portions. In particular, the support member 26 has been spaced at a somewhat greater distance from the spacer 30 and an annular bimetal washer 50 is inserted between the ceramic disc 28 and the support member 26. In determining the metals of which to make the bimetal washer 50 (or the bi-metallic element 38), one skilled in the art would choose one metal with a very low thermal coefficient expansion and the other metal with a high thermal coefficient of expansion. For example, one of the metals could be chosen as invar and the other metal could be chosen from brass, stainless steel (18-8), or silver. The ceramic disc 28, the spacer 30, the bimetal washer 50 and support member 26 have been arranged with respect to each other to provide a small but sufiicient play so that when the tube is in an inoperative condition the ceramic disc 28 and cathode shell 24 are free to be rotationally moved.

During the normal operation of the device shown in FIG. 5, the thermal energy emitted from heater element 36 would normally be sufficient to cause the bimetal washer 50 to expand or warp thereby taking up the small allowed play mentioned above. The pressure exerted by the bimetal washer 50 tends to prevent any further movement of the cathode shell 24 which is thereby locked in a fixed position relative to the grid cup 22. To release the cathode, the heater element is de-energized to allow the bimetal washer 50 to reassume a fiat or unflexed condition. In this condition, the electron emissive portion beneath the grid aperture 34 can be renewed by allowing substantially frictionless rotation of the cathode shell 24 by the bi-metallic element 38 as discussed above.

FIG. 6 shows another embodiment of this invention involving two bimetal washers whereby the ceramic disc 28 and the cathode shell 24 may be locked with respect to the grid aperture 34, while the electron tube 10 is in either an operative or inoperative condition. Further, this embodiment employs a simplified .means contained within the grid cup 22 for rotating the electron emissive layer 23. The arrangement of the ceramic disc 28, the cathode shell 24, the spacer 3t) and the grid cup 22 are essentially as described with respect to FIG. 2 above. The primary differences between this embodiment and that shown in FIG. 2 reside in the means for motivating the cathode shell 24 and the means for locking the cathode shell 24 and the ceramic disc 28 in place. A first bimetal washer 50a is inserted between a first support 26a and the ceramic disc 28. The first support 26a is of an annular configuration and is secured in place as by welding to the sides of the grid cup 22. Therefore, when the first bimetal washer 50a is in a flexed condition, the ceramic disc 28 will be held tightly between the first support 260 and the spacer 30. A second annular bimetal washer 50b is inserted between an annular, L-shaped intermediate member 52 and an annular disc member 54 which is placed on a second support 26b. The intermediate member 52 is not directly secured to the grid cup 22 and is free to move in an axial direction. The second support 2617 is secured to the sides of the grid cup 22 thereby holding the second disc member 54 and the second bimetal washer 50b in place. The disc member 54, as well as the ceramic disc 28, may be made of a heat resistant ceramic material such as alumina. One surface of the L-shaped intermediate spacer member 52 is placed against the second bimetal washer 5% whereas the end portion of the extended leg of the intermediate spacer member 52 is placed against the ceramic disc 28. Therefore, when the second bimetal washer Stlb is in a flexed condition the intermediate spacer member 52 will be pressed upward holding the ceramic disc 28 against spacer 3t and preventing the ceramic disc 28 from any axial or transverse movement. The second bimetal washer 50b is preflexed so that when the washer 50b is in a cold condition, i.e., the cathode heater 36 is unenergized, the second bimetal washer 50b will be in a flexed or bent condition. The first bimetal washer 50:; has not been preflexed, and therefore, when the cathode assembly 29 is in an inoperative condition the first bimetal washer 56a will be in a flat condition and will not exert a pressure against the ceramic disc 28. Therefore as a result of providing two bimetal washers and an intermediate spacer member 52, the ceramic disc 28 and the cathode shell 24 will be normally in a locked-in position while the electron tube is both operative and inoperative. In greater explanation, when the electron tube 16 is in an inoperative condition, the second bimetal washer 5% will be in a flexed condition thereby pressing the intermediate member 52 upwards to secure the ceramic disc 28 firmly against the spacer 30; when the electron tube is in an operative condition, the first bimetal washer 56a will then be in a flexed condition pressing the ceramic disc 28 firmly against spacer 30 regardless of whether the bimetal washer 5% is in a flexed or flattened condition.

A very simply and novel means has been provided in FIG. 6 to rotate the ceramic disc 28 and the cathode shell 24 in order to renew the emissive portion of layer 23. The motivating means consists of a mass 56 positioned on the ceramic disc 28 at a distance from the center axis of the cathode shell 24 so that when the ceramic disc 28 is released (as explained below), the cathode shell may be rotated by merely tapping the glass envelope 11 of the electron tube 1%. As shown in FIG. 6, the annular disc member 54 has embedded therein a reset heater 58 which is in thermal association with the second bimetal washer 56!). Therefore, when the electron tube 10 is in an inoperative condition, the reset heater 58 may be energized thereby thermally activating the second bimetal washer 56b to a straightened or an unfiexed condition with the result that the pressure normally exerted by the second bimetal washer 5% upon the intermediate member 52 and the ceramic disc 28 against spacer 30 will be released. As a result, when the reset heater 5% is activated the ceramic disc 23 may be released and the envelope 11 of the electron tube It; tapped or shaken to allow the offset mass 56 to rotate the ceramic disc 28 and the cathode shell 24, thereby renewing the emissive portion under the aperture 34.

To renew the cathode emissive portion of the device shown in FIG. 6, the following procedure may be used:

(A) The cathode heater 36 is deenergized and the electron tube 10 is placed in an inoperative condition thus allowing the assembly 26 to cool;

(B) The reset heater 58 is energized whereby causing the second bimetal washer 50b to assume a more straightened or flattened condition thereby removing pressure against the cathode disc 28;

(C) The envelope 11 is tapped so that the torque of the mass 56 mounted on the ceramic disc 28 will cause the cathode shell 24 to rotate about its axis;

(D) The cathode heater 36 is energized to cause the first bimetal washer 56a to lock the cathode shell 24 in position; and

(E) The reset heater 58 is de-energized thereby causing the intermediate spacer member 52 to reassume its normal position and to lock the ceramic disc 28 in place.

The tube 16 is now prepared for a new life cycle.

The embodiment of applicants invention disclosed in FIGS. 7 and 8 resemblies that described in FIG. 5; the grid cup 22, the cathode shell 24, the ceramic disc 28, the support member 26, the spacer 30 and the bimetal washer are similar in configuration and arrangement to those which have been previously described. In this embodiment, the ceramic disc 28 and the cathode shell 24 are caused to rotate beneath the grid aperture 34 by an annular eccentric washer which may be made of any suitable material such as stainless steel. The eccentric washer 663 is placed between the bimetal washer 50 and the spacer 36; the ceramic disc 28 is placed within the eccentric washer 60 in an offset hole 61. As can be more clearly seen in FIG. 8, the eccentric washer 69 has a plurality of ratchet teeth 63. The motivating means for the eccentric washer 6i and the ceramic disc 28 comprises a bi-metallic spiral coil 66 and its thermally associated coil heater 70. The spiral coil 66 is secured on its inwardmost end to a heater tube 64, which is in turn supported by supports 62 to the grid cup 22. The coil heater 7% is located within the heater tube 64. An engaging end 8 of the spiral coil 66 projects through the slot 41 and engages the ratchet teeth 63 located on the periphery of the eccentric washer 60. Further, a window 74 is provided through which a dog member 72 may extend to mesh with the ratchet teeth 63 of the eccentric washer 60; one end of the dog member 72 is secured to the outer surface of the grid cup 22.

One advantage of providing an eccentric washer 60 is that the sliding or brush type of connections (not shown) which would be necessary to make electrical contact with the cathode shell 24 of FIGS. 2 to 6 may be eliminated.

In the embodiments shown in FIGS. 2 to 6, a wire or connector could not be fixedly secured to the cathode shell 24 because during the changing of the emissive portion, the cathode shell 24 would be rotated about its axis. With regard to those embodiments shown in FIGS. 7 and S employing the eccentric washer 60, the emissive portion of layer 23 is renewed by rotating the eccentric washer 66. The rotation of the eccentric washer 6t) orbits the cathode shell 24 about the axis of the grid cup 22 thereby placing the various portions of layer 23 beneath the aperture 34. However, the cathode shell 24 does not revolve about its own axis, but remains unrotated as it moves about the center axis of the grid cup 22. Thus, a sliding contact is not needed and a wire 24a may be directly secured to the cathode shell by any suitable means known in the art such as welding.

The embodiment disclosed in FIGS. 7 and 8 can be operated so as to renew the cathode emissive portion in any of several modes. In one mode, while the electron tube 19 is in an inoperative condition, i.e., the cathode heater 36 is de-energized, the coil heater '70 is energized thereby causing the spiral coil 66 to flex and its engaging end 68 to move downward (as seen in FIG. 8) to engage the ratchet teeth 63 thereby rotating the eccentric washer 60.

As a result of the rotational movement (which is only a fraction of a revolution) undergone by the washer 66, the ceramic disc 28 will take a new position previously occupied by the eccentric hole 61 and consequently a different cathode surface will be facing the grid aperture 34. While the spiral coil 66 is contracting on being cooled, the dog member 72 prevents the eccentric washer 60 from moving in a counterclockwise motion. The dog member 72 could in principle be omitted siince the operator could prevent the eccentric washer 60 from rotating clockwise or counterclockwise by energizing the cathode heater 36 and causing the bimetal washer 50 to lock the ceramic disc 23 in place. In a second mode, an automatic operation could be achieved by connecting the coil heater 70 and the cathode heater 36 in parallel so that both heaters may be switched on at the same time. The basic consideration in this mode would be to have the spiral coil 66 to react before the bimetal washer 50 flexes to lock the ceramic disc 28 and the eccentric washer 66 in place. This could be achieved by varying the relative heating capacity of the cathode heater 36 and the coil heater 70 or by selecting the constituent metals so that the bi-rnetallic spiral coil 66 responds at a faster rate than the bimetal washer 50. In operation, a voltage would be applied simultaneously to both the cathode and the coil heaters 36 and 70 respectively; the spiral coil 66 would respond first thereby rotating the eccentric washer 69 in a clockwise direction and causing the ceramic disc 28 to move laterally as described above. (See FIG. 8). As the bimetal washer 56 responds to the heat generated by the cathode heater 36, it will lock the ceramic disc 28 in a new position. The coil heater 7% may then be turned off after the ceramic disc 28 has been locked in place or it may simply be left on. When the cathode heater 36 and the coil heater 79 are de-energized the dog member 72 would prevent the spiral coil 66 from rotating the eccentric washer 60 in a counterclockwise direction. In a third mode, the cathode shell 24 could be rotated during the period in which the cathode heater 36 is warming up. The basic consideration in this mode would be to design the bimetal washer 56 so as to have a preflexed or biased condition. Therefore, when the bimetal washer 56 is in a cold condition, it would be flexed so to lock the ceramic disc 28 into position. Further, the washer 59 while being heated will go from a flexed condition in one direction to a flexed condition in the other passing through a relatively flat or unflexed condition. It is during this transitional unflexed condition of the bimetal Washer 59 that the coil heater 70, which has been energized in advance, will cause the spiral coil 66 to rotate the eccentric washer 60. Further, the washer 56 could be maintained in an unflexed condition for any desired length of time by applying a suitably reduced voltage to the cathode heater 36. The renewing of the emissive portions could be determined by external circuitry involving counters or timers without the need of an operator manually switching the circuits on.

In FIG. 9, there is shown another embodiment of this invention in which the cathode shell 24 motivator comprises a helical coil 76 which is mounted on a heater tube 64 with a coil heater 70 positioned within the tube 64. One end of the helical coil 76 is secured to the heater tube 64 whereas the other end of the helical coil 76, the engaging end 68, meshes with the ratchet teeth 63 of the eccentric washer 60 through the slot 41 of the grid cup 22. It is further suggested that the coil heaters '70 and 40 can be eliminated in their respective embodiments; the bimetal strips (such as coils '76, 66 and element 38) can be heated directly by current flowing across its length by applying a voltage difference across the ends of the strips.

In FIG. another embodiment of this invention is shown in which an electromagnetic means is used to motivate the ceramic disc instead of a thermal responsive means. More specifically, a pawl member 78 is so positioned so as to extend through slot 41 into engagement with the ratchet teeth 63 of the eccentric washer 69. The other end of the pawl member 7 8 is rigidly secured to the grid cup 22. A magnetic coil 84 is wound about a magnetic core 82 and the combination is placed exteriorly of the glass envelope 11 and in magnetic relation to a bar or member 80 of soft magnetic material which is secured to the pawl member 78. By alternatively switching the magnetic coil 84 on and off the pawl member 78 may be vibrated so as to effect a rotation of the eccentric washer 60. Further, the bar 80 of soft magnetic material and the pawl member 78 could be tuned to resonate at the frequency of the AC. voltage applied to the magnetic coil 84. In explanation, an analogy may be made between the pawl member 78 and bar 8-9, and a tuning fork. As in a tuning fork, the mass and the length of the pawl member 78 and the mass of the bar 80 maybe adjusted so as to resonate at a given frequency i.e., the frequency of the AC. voltage applied to the magnetic coil 84. Thus, by applying a voltage of a given frequency to the magnetic coil, the eccentric washer 66 would slowly rotate as long as the operator applied the voltage. In this manner, a magnetic means could be used to rotate 8 the eccentric washer and thereby cause the electron emissive layer 23 upon the cathode shell 24 to move beneath the grid aperture 34.

In FIGS. 11 and 12, a simplified embodiment of applicants invention is shown whereby the electron emissive portion of the cathode may be renewed in an entirely automatic fashion. The grid cup 22, the ceramic disc 28, the cathode shell 24, the eccentric washer 64 the bimetal washer 5t) and the support member 26 are similar in structure and arrangement to the elements described and shown in FIG. 7. In the embodiment of FIGS. 11 and 12, an annular spacer is mounted to rotate freely within the grid cup 22 when the device is in an inoperative or cold condition. A vertical portion of the spacer 90 rests against the enclosed end of the grid cup 22 Whereas the horizontal portion abuts the eccentric washer 60 and the ceramic disc 23. Ascan be seen in FIG. 11, a portion of the spacer 96 is bent downward to form a locking tab 94 which fits into a slot 96 in the eccentric washer 66. The means for rotating the cathode shell is provided by a spiral bi-metallic coil 92. A fixed end 102 of the spiral coil 92 is secured to the vertical portion of the spacer 90 by any suitable means known in the art such as spot welding. The other end of the spiral coil 92, the engaging end 196, is allowed to move along the inner periphery of the grid cup 22. A plurality of detents 98 are bent inward from the inner periphery of the grid cup 22 so as to engage the hook-like engaging end 100 of the spiral coil 92.

The embodiment of FIGS. 11 and 12 operates so as to move around the cathode shell 24 beneath the aperture 34 so as to renew the electron emissive portion each time the heater element 36 is energized. When voltage is applied to the heater element 36, the heat emanating therefrom will cause the bimetal washer 5% to expand and lock the ceramic disc 28. At the same time, the thermal energy from heater element 36 will also cause the spiral coil 92 to flex thereby causing the engaging end to move in a clockwise rotation (as seen from the top of the grid cup 22 in FIG. 12). The engaging end of the spiral coil 92 will slip freely past the detents 98 as long as the spiral coil 92 is expanding in a clockwise rotation. The spiral coil 92 will remain in an extended position as long as the device is in an operative condition. When the heater element 36 is de-energized, both the spiral coil 92 and the bimetal washer 50 will begin to cool. As a result, the spiral coil 92 will begin to contract with its engaging end 100 catching in one of the detents 98 thereby causing a stress in the spiral coil 92 which increases as the cooling progresses. As the cathode assembly 20' continues to cool, the bimetal washer 56 will tend to assume its unflexed condition and will gradually release the eccentric washer 6 and the ceramic disc 28. When the torque applied by the stressed spiral coil 92 upon the spacer 90 is sufiicient to overcome the locking force placed on the spacer 90 by the bimetal washer 50, the spiral coil 92 will contract and cause the coupled spacer 90 to follow it. In turn, the spacer 9t will likewise cause the eccentric washer 69 to rotate, and as a result, the ceramic disc 23 will move into the new position taken by the eccentric hole 61. In this manner, the electron emissive layer 23 beneath the aperture 34 will be renewed each time the electron tube is operated.

In FIG. 13, there is shown another automatic embodiment of this invention, the structure of which is essentially similar to that shown and described in FIGS. 7 and 8. It is noted that this embodiment does not have a coil heater for a bi-metallic spiral coil 104 nor does it have a dog member. Rather, the spiral coil 104 is thermally energized by the waste heat from the cathode heater element 36. Unlike the previous automatic embodiments, the spiral coil 104 is arranged outside of the grid cup 22 on a coil support 166. One end of the spiral coil 104 is secured to the coil suport 106, whereas the other end, a hook-like end 168, is disposed through slot 41 of the grid cup 22 thereby engaging the ratchet teeth 63 of the eccentric washer 60. In operation, the cathode heater element 36 is energized thereby heating progressively both the bimetal washer (see FIG. 7 for placement) and also the spiral coil 104. In this embodiment the bimetal washer 50, since it is in closer thermal proximity to the heater element 34 than the spiral coil 1G4, will react before the spiral coil 104 and lock the eccentric Washer 60 and the ceramic disc 28 in place before the spiral coil 1% can respond to the thermal energy from the heater element 36. After the bimetal washer 50 has locked the eccentric washer 60 in place, the spiral coil 104 will begin to expand and flex so that the hook-like end 108 will begin to slide past the ratchet teeth 63 of the eccentric washer 69. When the spiral 104 has reached its maximum expansion, it will stay in this position as long as the tube is in an operative condition. When the electron tube is allowed to cool, the hook-like end 1% will start the reverse movement and engage one of the ratchet teeth 63 of the eccentric washer 60, thus placing an increasing torque on the washer fit) as the assembly cools. When the bimetal washer 59 releases the eccentric washer 60, and the ceramic disc 28, the spiral coil 104 will effect the desired rotational movement and displace the emissive portion on the cathode shell 24 beneath the aperture 34. Thus, with the above embodiment the cathode emissive portion will be renewed after each time the electron tube has been operated without need of a separate operation.

It will therefore be apparent that there has been disclosed a very simple and inexpensive means for rotating the cathode assembly to renew that portion of the electron emissive layer beneath the aperture of the grid face. By simply rotating or displacing the cathode shell about an offset axis with respect to the grid aperture a new portion of the electron emissive layer may be employed as a source of an electron beam. Another means for renewing a cathode emissive portion employing an elongated filament is shown in a co-pending application Serial No. 360,268, entitled Electronic Tube Device to E. Atti and assigned to the assignee of this invention.

It is noted that though all of the electron emissive layer 23 is being excited by the cathode heater element 36, it is principally the portion of the layer 23 beneath the apertures 34 that will be dissipated. This results from the fact that the current drawn from the cathode shell 24 to form the electron beam emanates from that portion of the layer 23 facing the aperture 34.

While there have been shown and described What are at present considered to be the preferred embodiments of the invention, modifications thereto will readily occur to those skilled in the art. It is not desired therefore, that the invention be limited to the specific arrangements shown and described and it is intended to cover in the appended claims all such modifications that fall within the true spirit and scope of the invention.

I claim as my invention:

1. An electron discharge device comprising an envelope having therein a source for producing an electron beam, said source having at least a first and second portion, a control element having an aperture therein,.said aperture so positioned with respect to said source so that said first portion substantially emanates all of said electron beam, means for moving said source with respect to said aperture so that said second portion emanates substantially all of said electron beam rather than said first portion, and locking means for disposing said source in a fixed position with respect to said aperture and for releasing said source to thereby allow said means for moving to freely move said source.

2. An electron discharge device comprising an envelope having therein a sOurce for producing an electron beam, said source having a plurality of emissive portions, a target means tor receiving said electron beam, said source being movably mounted, a control element disposed between said source and said target means and having an aperture therein, said aperture overlying one emissive portion of said source so that said one emissive portion emanates substantially all of said electron beam, said source including a first heating means for activating said source, said first heating means being associated with a first thermal responsive locking means, said first locking means being so disposed as to secure said source while said electron discharge device is in an operating mode, a second thermal responsive means being disposed so as to secure said source when said electron discharge device is in a non-operating mode, a second heating means associated with said second locking means and insulated from said first locking means, and a means for selecting another emissive portion so that said other portion substantially emanates all of said electron beam rather than said one portion.

3. An electron discharge device comprising an envelope having therein a source for producing an electron beam said source having at least a first and second portion, a target means for receiving said electron beam, said source being moved about an axis, a control element disposed between said source and said target means and having an aperture therein spaced from said axis, said first portion emanating substantially all of said electron beam, said source including a first heating means for activating said source and associated with a first thermal responsive locking means, said first locking means being so flexed as to secure said source with respect to said aperture while said electron discharge device is in an operating mode, a second thermal responsive locking means associated with said first heating :means, said second thermal responsive means being flexed as to secure said source with respect to said aperture when said electron discharge device is in a non-operating mode, a second heating means associated with said second locking means and insulated from said first locking means, and a means for selecting said second portion so that said second portion substantially emanates all of said electron beam rather than said first portion, said means for select ing comprising a mass connected to said source and spaced from said axis, said means for selecting being operable when the first heating means is in an oif condition and said second heating means has been energized so as to release said second thermal locking means.

4. An electron discharge device comprising an envelope, a source for producing an electron beam, said source having at least first and second portions, a target means for receiving said electron beam, a control element disposed between said source and said target means and having an aperture therein, said first portion substantially emanating all of said electron beam, means for substituting said second portion for said first portion so that said second portion emanates substantially all of said electron beam rather than said first portion, and thermal responsive locking means for fixing the position of said source with regard to said aperture and for releasing said source to allow said means for substituting to move said source.

5. An electron discharge device comprising an envelope having therein a source for producing an electron beam, said source having at least first and second portions, target means for receiving said electron beam, a control element disposed between said source and said target means, said control element having an aperture therein, said aperture overlying said first portion of said source, said first portion substantially emanating all of said electron beam, said source being movably mounted with respect to said aperture, means Within said envelope for selecting said second portion beneath said aperture so that second portion emanates substantially all of said electron rather than said first beam, heating means, and locking means responsive to said heating means for fixing the position of said source with respect to said control element and for releasing said source to allow said means for selecting to impart a relative movement between said source and said control element.

6. A cathode assembly comprising a source for producing an electron beam, said source having first and second emissive portions, a control element having an aperture therein, said aperture so positioned with respect to said source so that said first emissive portion emanates substantially all of said electron beam, means for moving said source with respect to said control element so that said second emissive portion emanates substantially all of said electron beams rather than said first emissive portion, and means for fixing the position of said control element with respect to said source and for releasing said source to allow said means for moving to move said source.

7. A cathode assembly substantially as claimed in claim 6, wherein said means for moving is so constructed to react before said means for fixing.

8. A cathode assembly substantially as claimed in claim 6, wherein said means for fixing is so constructed to react before said means vfor moving.

9. An electron discharge device comprising an envelope having therein a source for producing an electron beam, said source having a plurality of emissive portions, target means for receiving said electron beam, a control element disposed between said source and said target means having an aperture therein, one of said emissive portions substantially emanating all of said electron beam, locking means for securing said source with respect to said aperture and for releasing said source, and means for substituting another of said emissive portions so that said other emissive portion emits substantially all of said electron beam rather than said one portion, said locking means so constructed to respond after said means for substituting secures said source, and detent means to prevent said source from being returned to its original position by said means .for substituting.

10. An electron discharge device comprising an envelope having therein a source for producing an electron beam, said source having first and second emissive portions, target means for receiving said electron beam, a control element disposed between said source and said target means having an aperture therein, said first emissive portion substantially emanating all of said electron beam, first heating means, thermal responsive locking means for securing said source with respect to said control element and for releasing said source to allow said source to be moved, said thermal responsive locking means 'being thermally associated with said first heating means, thermal responsive means for substituting said second emissive portion so that said second emissive portion emits substantially all of said electron beam rather than said first portion, and second means for heating thermally associated with said means for substituting.

11. An electron discharge device substantially as claimed in claim 10, wherein a detent means prevents the source from being returned to its original position by said means for substituting.

12. An electron discharge device comprising an envelope having therein a source for producing an electron beam, said source having a plurality of emissive portions, target means for receiving said electron beam, a control element disposed between said source and said target means, said control element having an aperture therein, one of said plurality of emissive portions substantially emanating all of said electron beam, thermal responsive means for locking said source with respect to said control element and for releasing said source to allow said source to be moved, thermal responsive means for substituting another emissive portion so that said other portion emanates substantially all of said electron beam rather than said one portion, means for producing heat in thermal association with said means for locking and said means for substituting, detent means positioned in fixed relation rwith said control element, one end of said means for substituting being secured to said source whereas said other end of said means for substituting being free to move with respect to said detent means.

13. An electron discharge device comprising an envelope having a cathode assembly for producing an electron beam and a target means for receiving said electron beam, said cathode assembly comprising a hollow grid cup having an enclosed end with an aperture therein, a cathode cylinder having an emissive layer disposed on an enclosed end thereof, an insulating disk having an opening therein into which the cathode cylinder is placed, an annular member for spacing said cathode cylinder from said enclosed end of said grid cup and for positioning said insulating disk and cathode cylinder so that the center axis of said cathode cylinder is offset from said aperture, a bi-metallic washer placed against said insulating disk, and a support member fixedly secured to said grid cup so as to hold said bi-metallic washer against said insulating disk.

1 An electron discharge device comprising an envelope having therein a cathode assembly producing an electron beam, a target means for receiving said electron beam, said cathode assembly including a hollow grid cup having an enclosed end with an aperture therein, a cathode shell having an enclosed end with an emissive layer thereon, said cathode shell being disposed within said grid cup with said emissive layer disposed beneath said aperture, and a bi-metallic element having one end thereof operatively secured to said cathode shell and its other end in association with a plurality of detent means arranged on the inner periphery of said grid cup, and a bi-metal member for fixing the position of said cathode shell with respect to said grid cup and for releasing said cathode shell to allow said cathode shell to be moved by said bi-metallic element.

15. An electron discharge device comprising an envelope having therein a cathode assembly for providing an electron beam, target means for receiving said electron beam, said cathode assembly including a hollow grid cup having an enclosed end with an aperture therein, a cathode shell having an enclosed end with an emissive layer thereon, an insulating disk with an opening therein for receiving said cathode shell, an annular member for spacing said insulating disk from the enclosed end of said grid cup so that said cathode shell is disposed with its enclosed end beneath said aperture, a bimetal washer disposed against said insulating disk for fixing the position of said cathode shell with respect to said aperture and for releasing said cathode shell to allow said cathode shell to be moved, a support member fixedly secured to the inner periphery of said grid cup to hold the bimetal washer against the insulating disk, and a spiral bi-metallic element having one end secured to said annular member and its other end in association with a plurality of detent means arranged on the inner periphery of said grid cup, said annular member being operatively secured to said insulating disk.

16. An electron discharge device comprising a source for producing an electron beam, said source having at least first and second portions, target means for receiving said electron beam, 21 control element disposed between said source and said target means and having an aperture therein, said first portion substantially emanating all of said electron beams, means for substituting said second portion for said first portion so that said second portion emits substantially all of said electron beam rather than said first portion, and first and second thermal responsive locking means for fixing the position of said source with regard to said aperture, said first and second thermal responsive locking means being so constructed to secure said source during different periods of time.

17. An electron discharge device as claimed in claim 16, wherein there is included a heating means associated with at least one of said locking means to allow said one locking means to release said source.

18. An electron discharge device comprising a source for producing an electron beam; said source having first and second emissive portions; target means for receiving said electron beam; a control element disposed between said source and said target means and having an aperture therein; said first emissive portion substantially emanating all of said electron beam; means for exerting a force tending to move said source with respect to said control element; and locking means for securing the relative position of said source with respect to said control element While said means for exerting establishes a force upon said control element and said source, and for releasing said source to thereby allow said means for exerting to impart a relative motion between said source and said control element.

19. An electron discharge device as claimed in claim 18, wherein there is included a heater element, said locking means being responsive to the thermal energy generated by said heating means.

20. An electron discharge device as claimed in claim 19, wherein said means for exerting a force is responsive to the thermal energy generated by said heating means,

said locking means being so constructed to respond before said means for exerting a force.

References Cited by the Examiner UNITED STATES PATENTS 2,825,838 3/1958 Charles 313-337 X 3,197,665 7/1965 Cope 313-270 FOREIGN PATENTS 886,636 8/1953 Germany.

References Cited by the Applicant UNITED STATES PATENTS 2,175,582 10/1939 Vogel et al, 3,099,762 7/1963 Hertz. 3,109,953 11/1963 Burnett.

JOHN W. HUCKERT, Primary Examiner.

A. 1. JAMES, Assistant Examiner. 

1. AN ELECTRON DISCHARGE DEVICE COMPRISING AN ENVELOPE HAVING THEREIN A SOURCE FOR PRODUCING AN ELECTRON BEAM, SAID SOURCE HAVING AT LEAST A FIRST AND SECOND PORTION, A CONTROL ELEMENT HAVING AN APERTURE THEREIN, SAID APERTURE SO POSITIONED WITH RESPECT TO SAID SOURCE SO THAT SAID FIRST PORTION SUBSTANTIALLY EMANATES ALL OF SAID ELECTRON BEAM, MEANS FOR MOVING SAID SOURCE WITH RESPECT TO SAID APERTURE SO THAT SAID SECOND PORTION EMANATES SUBSTANTIALLY ALL OF SAID ELECTRON BEAM RATHER THAN SAID FIRST PORTION, AND LOCKING MEANS FOR DISPOSING SAID SOURCE IN A FIXED POSITION WITH RESPECT TO SAID APERTURE AND FOR RELEASING SAID SOURCE TO THEREBY ALLOW SAID MEANS FOR MOVING TO FREELY MOVE SAID SOURCE. 